1. Field of the Description
The present description relates, in general, to design and control of ride platforms, and, more particularly, to a six degree of freedom (DOF) motion platform for use in amusement park rides and other applications that is configured to have redundant load paths.
2. Relevant Background
It is often desirable in the design of amusement or theme park rides (and other applications) to provide a six DOF motion platform for supporting a passenger or ride vehicle. Six DOF motion refers to freedom of movement of a rigid body (e.g., the motion platform for supporting a ride vehicle (or the motion platform may be the base of the vehicle)) in three-dimensional (3D) space. The rigid body can be moved via driving or actuation of the motion platform to change position with forward/backward, up/down, and left/right translation in three perpendicular axes combined with changes in orientation through rotation about three perpendicular axes (or through pitch, yaw, and roll).
Ride designers have commonly used a Stewart platform to implement a six DOF motion platform to support and selectively move a ride vehicle. A Stewart platform is a type of parallel robot or mechanism that incorporates six linear actuators or jacks. These actuators are mounted in pairs to the mechanism's stationary support base at one end and a top plate or motion platform at a second end. Objects such as a ride vehicle placed on the top plate or motion platform can be moved in the six degrees of freedom in which it is possible for a freely-suspended body to move (i.e., three linear movements (along the X, Y, and Z axes or with lateral, longitudinal, and vertical movement) and three rotations of pitch, roll, and yaw).
In these rides or ride systems, the Stewart platform motion base is configured in a triangular, six-member truss arrangement where each member is a linear actuator. While this design allows for effective manipulation of the motion platform with six degrees of freedom, each member or component (e.g., linear actuator) in all of the six truss members is a non-redundant load path. For ride system applications, non-redundant load path components are a major safety concern. In order to maintain a safe and stable structure for riders in the vehicle on the motion platform, it is important that none of the components can fail without causing catastrophic instability to the motion platform, but this is not the case with a conventional Stewart platform motion base. For example, failure of any one of the linear actuators (or even a pin or subcomponent of the actuator) will cause the motion platform to become unstable. Due to the non-redundancy associated with use of Stewart platforms, it is necessary for the ride system to be designed with very high factors of safety for strength and fatigue. Additionally, the typical Stewart platform-base ride system is typically designed to include additional mechanical or structural components in order to maintain structural safety in the event of a truss component failure.
Another problem with the use of a triangular motion platform (three connection points between actuator pairs and motion platform form a triangle) is that the majority of ride vehicles (e.g., vehicle bodies such as a ride simulator cabin) are rectangular rather than triangular. Hence, the ride system is made more complex as use of a Stewart platform often necessitates the addition of an extra structural base to be mounted on top of the motion platform, which adds weight and complication to the ride system.
Hence, there remains a need for an improved motion platform that can provide six DOF motion and is especially well-suited for use as a motion platform for an amusement or theme park ride.